5.19 Burst Transmission (TX_ON)

Pin

 

Name

 

Direction

 

Function

 

 

 

 

 

 

 

35

 

TX_ON

 

Output

 

Transmit indication

Burst transmission is the period during which the GSM transceiver is transmitting RF signals. TX_ON is an indicator that the module is transmitting.

A typical application may use TX_ON to blank adjacent receiver circuitry as a means of protecting sensitive input stages. TX_ON is active HIGH.

5.20 Real Time Clock

The real-time clock (RTC) is driven by a 32.768 kHz clock from an internal crystal oscillator. The clock is divided by 32,768 to generate a clock with a 1 second period that increments a 29-bit seconds counter. In addition, it can generate interrupts at a programmed time. The following are the features of RTC:

•17-year time interval with 1 second resolution.

•Programmed time alarm interrupt

•Alarm output pin

An RTC alarm can be set by loading an appropriate value into the seconds alarm register and enabling an interrupt via an AT-command.

The RTC relies on an uninterrupted 1.5 V (nominal) power supply (VRTC), whether the module is powered off or on. The RTC alarm operates from the VRTC supply, and therefore utilize 1.5 V logic. Users have the responsibility to provide a backup battery to provide uninterrupted VRTC function when the module is powered down.

RTC Accuracy

Parameter

 

Condition

 

Max

 

Unit

 

 

 

 

 

 

 

RTC accuracy

 

Ambient (+25±2°C) operation

 

52.6

 

Secs/month

RTC accuracy

 

Extreme temperatures

65.2

 

Secs/month

LZT 123 1834

70